There have been developed disposable cooking thermometers particularly useful in cooking meat and poultry to a proper or desire degree of "doneness". One type of such a timer has a spring-loaded stem disposed in a hollow barrel and normally held therein by locking the inner stem end in a fusible material which melts or softens at a desired predetermined temperature. It is desirable, and generally necessary, to ensure retention of the fusible material within the barrel of the timer to prevent possible contamination of the meat or poultry in which the timer is inserted. Various types of sealing arrangements have been proposed to this end and a wide variety of stem locking arrangements have been developed. At least certain of these arrangements and developments have been directed to minimizing the complexity and cost of the timer because this type of timer must necessarily have a low cost inasmuch as it is disposable.
It is also necessary for this type of timer to be highly reliable, for otherwise overcooking or undercooking of meat or poultry will result. Consequently, precise assembly of small parts is required as well as careful control of the properties of the fusible material. Another possible cause of unreliable operation arises from the nature of the environment of assembly and use of the timer. In the processing of poultry, for example, it is common to subject the carcass to successive baths of differing liquids that may include butter or butter substitute, brine, etc. Also in the cooking of poultry there are released juices and fats that may harden during continued exposure to elevated temperatures. The various liquids that may come in contact with a time during the life thereof, as generally noted above, could affect operation of the timer if allowed to enter the barrel of same. Thus it is also important to seal the timer against liquids entering same prior to actuation of the timer to extend the stem thereof. Most timers of this of type do not fully seal the interior thereof from intrusion of foreign substances into the barrel without the provision of additional elements and structure beyond that required for proper operation in a dry environment. This then reduces the overall reliability of disposable cooking thermometers or timers.